Association between changes in habitual physical activity and changes in bone density, muscle strength, and functional performance in elderly men and women

OBJECTIVES: To investigate the long-term effects of habitual physical activity on changes in musculoskeletal health, functional performance, and fracture risk in elderly men and women.

DESIGN: Ten-year prospective population-based study.

SETTING: Malmö-Sjöbo Prospective Study, Sweden.

PARTICIPANTS: Participants were 152 men and 206 women aged 50, 60, 70, and 80 who were followed for 10 years.

MEASUREMENTS: Distal radius bone mineral density (BMD) (single photon absorptiometry), upper limb muscle (grip) strength, balance, gait velocity, occupational and leisure-time activity, and fractures (interview-administered questionnaire) were reassessed after 10 years. Annual changes for all measures were compared between participants with varying habitual physical activity histories at baseline and follow-up: inactive–inactive (n=202), active–inactive (n=47), inactive–active (n=49), and active–active (n=60). Data for men and women were pooled, because there were no sex-by-activity group interactions. To detect possible differences in fracture incidence between the varying habitual activity groups, participants were classified into two activity groups based on their activity classification at baseline and follow-up: inactive:less active versus active:more active.

RESULTS: The annual rate of bone loss was 0.6% per year less in individuals classified as active at both time points than in those classified as inactive at both time points (P<.01). Similar results were observed for balance, but there was no effect of varying habitual activity on changes in muscle strength or gait velocity. There were also no differences in fracture incidence between individuals categorized as active:more active and those categorized as inactive:less active during the follow-up (adjusted hazard ratio=0.90, 95% confidence interval (CI)=0.42–1.90).

CONCLUSION: This study showed that elderly men and women who maintained a habitually active lifestyle over 10 years had lower bone loss and retained better balance than those who remained habitually inactive.

Strength training of one limb increases corticomotor excitability projecting to the contralateral homologous limb

The contralateral transfer of strength following unilateral strength training (ULS) is thought to be due to changes within the nervous system. Using transcranial magnetic stimulation (TMS) we compared corticospinal responses following ULS of the right biceps brachii (BB) projecting to the untrained left BB. Motor evoked potentials (MEPs) were recorded from both BB of 23 individuals pre and post 4 weeks heavy load (80% of 1RM) ULS of right BB. TMS was delivered at intensities below active motor threshold (AMT) to saturation of the MEP (MEP_max). ULS resulted in a 28% increase in 1RM right BB strength, resulting in a 19.2% increase in contralateral strength of the left BB (p = .0001). There was a significant increase in MEP amplitude of 30.3% (p = .03), 33% (p = .05), and 26.5% (p = .01) at AMT, 20% above AMT and MEP_max respectively. No significant differences in silent period were seen at AMT, 20% above AMT or MEP_max. This study has demonstrated increased corticospinal excitability projecting to the untrained arm following heavy load ULS.

What has transcranial magnetic stimulation taught us about neural adaptations to strength training? A brief review

The evidence for neural mechanisms underpinning rapid strength increases has been investigated and discussed for over 30 years using indirect methods, such as surface electromyography, with inferences made toward the nervous system. Alternatively, electrical stimulation techniques such as the Hoffman reflex, volitional wave, and maximal wave have provided evidence of central nervous system changes at the spinal level. For 25 years, the technique of transcranial magnetic stimulation (TMS) has allowed for noninvasive supraspinal measurement of the human nervous system in a number of areas such as fatigue, skill acquisition, clinical neurophysiology, and neurology. However, it has only been within the last decade that this technique has been used to assess neural changes after strength training. The aim of this brief review is to provide an overview of TMS, discuss specific strength training studies that have investigated changes, after short-term strength training in healthy populations in upper and lower limbs, and conclude with further research suggestions and the application of this knowledge for the strength and conditioning coach.

Performance of suspended and attached growth MBR systems in treating high strength synthetic wastewater

The performance of laboratory-scale attached growth (AG) and suspended growth (SG) membrane bioreactors (MBRs) was evaluated in treating synthetic wastewater simulating high strength domestic wastewater. This study investigated the influence of sponge suspended carriers in AG-MBR system, occupying 15% reactor volume, on the removal of chemical oxygen demand (COD), total nitrogen (TN) and total phosphorus (TP), and compared it to that of SG-MBR. Results showed that the removal efficiencies of COD, TN and TP in AG-MBR were 98%, 89% and 58%, respectively as compared to 98%, 74% and 38%, respectively in SG-MBR. Improved TN removal in AG-MBR systems was primarily based on simultaneous nitrification and denitrification (SND) process. These results infer that the presence of small bio-particles having higher microbial activity and the growth of complex biomass captured within the suspended sponge carriers resulted in improved TN and TP removal in AG-MBR.

Effect of tool speeds during friction stir lap welding on mode of fracture and fracture strength of Al 6060-T5 joints

Friction stir lap welding (FSLW) of an age hardened Al alloy and evaluations of how FS speeds affected hooking and how hooking and softening due to FS affected fracture strength of the lap welds have been conducted. It was found that increasing rotation speed and reducing welding speed (v) increased the stir zone size (AB-SZ) and also hook size (h), although a maximum value of h (hMax) reached. The features of hooks for the observed - AB-SZ-h relationships are presented and explained. It was found that when h increased to a value of ~ 0.9 mm (for the 3 mm alloy sheets), it started to invoke a significant effect on reducing fracture strength. Factors such as FS softening and insufficient joining, limited the fracture strength of the lap welds for small h values and these are presented and discussed.

Understanding the behavior of advanced high-strength steels using atom probe tomography

The key evidence for understanding the mechanical behavior of advanced high strength steels was provided by atom probe tomography (APT). Chemical overstabilization of retained austenite (RA) leading to the limited transformation-induced plasticity (TRIP) effect was deemed to be the main factor responsible for the low ductility of nanostructured bainitic steel. Appearance of the yield point on the stress-strain curve of prestrained and bake-hardened transformationinduced plasticity steel is due to the unlocking from weak carbon atmospheres of newly formed during prestraining dislocations.

Application of advanced analytical techniques to study structure-property relationship of hot rolled high strength low alloy steel

The microstructure-property relationship in conventional high strength low alloy (HSLA) steel was evaluated using data obtained from transmission electron microscopy (TEM) and atom probe tomography (APT). Atom probe tomography allowed the characterisation of fine TiC particles with average radius of 3±1·2 nm that were not observed by TEM. The increase in the yield strength of steel due to the presence of fine precipitates was calculated to be 128 MPa.